它适用于 Chrome 和其他浏览器,但不适用于 Safari
<script>
var lastScrollTop = 0;
var navbar = document.getElementById("navbar");
window.addEventListener("scroll", function(){
var scrollTop = window.pageYOffset ||
document.documentElement.scrollTop;
if (scrollTop > lastScrollTop){
navbar.style.top="0px";
}else{
navbar.style.top="-120px";
}
lastScrollTop = scrollTop;
})